A known rotation detection sensor is disclosed in Japanese Patent Laid-Open Publication No. 2000-310646. This rotation detection sensor includes a holder accommodated in a case body having a bottom. The holder has a sensor and electronic parts, and is provided with a terminal by insert forming. A housing having a connector and an external peripheral groove extending in a circumferential direction of the case body is formed in a unitary manner on the case body. A welding portion provided on the case body during the molding process is welded when post forming the housing to maintain the sealing performance. This sealing prevents the oil in the housing, which accommodates a rotation member, from leaking to the connector side.
Another rotation detection sensor is also disclosed in Japanese Patent Laid-Open Publication No. 2000-310646. In this rotation detection sensor, in addition to the sealing provided by welding the welding portion upon post forming the housing, an additional sealing function relative to the case body is provided on the holder side. A groove is formed on the external periphery of the holder and a sealing member such as an O-ring is provided in the groove. Furthermore, a recess portion is provided on a holder in which the terminal extends in the longitudinal direction. By applying resin potting or fitting a rubber bush in the recess portion, the sealing of the recess portion is performed. Thus, a double sealing construction is provided relative to the sensor.
In the case of the first rotation detection sensor mentioned above and described in Japanese Patent Laid-Open Publication No. 2000-310646, because the welding portion is positioned on the rotation member side relative to the sealing member provided on the external peripheral groove, the case body is compressed by the pulsing hydraulic pressure under the installing condition in which the oil with high temperature and high pressure affects a tip portion of the rotation detection sensor. Thus, a drawback exists in that the welding portion may be destroyed by the stress applied to the welding portion, and this can cause oil to invade into the sensor.
In the case of the second rotation detection sensor mentioned above and described in Japanese Patent Laid-Open Publication No. 2000-310646, the invasion of oil into the sensor (i.e., the Hall IC accommodation space) is prevented in some respects by the sealing member provided at the recess portion formed on the holder. Notwithstanding this, because the sealing between the holder and the terminal is performed by resin potting, a drawback exists in that the attachment surface of the potting may peel off from the terminal due to the pulsating oil which is under high temperature and high pressure. This can cause the infiltration of oil into the sensor via a clearance between the terminal and the holder.
With the known rotation detection sensors mentioned above and described in Japanese Patent Laid-Open Publication No. 2000-310646, it is necessary to increase to some extent the resin pressure during pouring of the resin into the die for resin forming to prevent defective molding of the resin such as underfilling during post forming of the housing of the rotation detection sensor. However, because the resin pressure is applied to the rear end surface of the holder, the holder is compressed toward the detection element side. This can cause defects such as the deformation of the case body.
Additionally, in the aforementioned known rotation detection sensors mentioned above, the case body and the housing are fixed by supplying the resin for the housing to a stopper portion provided on the body case. Because the stopper portion is thin-walled and corresponds to the final destination of the resin, it is necessary to maximally increase the resin pressure at the post forming of the housing. However, with the second rotation detection sensor mentioned above, because the sealing member is positioned inside the position on which the stopper portion is provided, the forming resin pressure deforms the internal diameter of the case not to ensure a squeezing of the sealing member, and this is apt to cause a sealing defect.
A need thus exists for a rotation detection sensor whose tip portion is exposed to the high temperature and high pressure fluid and which is able to inhibit or prevent the invasion of the fluid therein.